Shatapatha Brahmana 1.1.4.15

1.1.4.15

tau hocatuḥ | śraddhādevī vai manurāvaṃ nu vedāveti tau hāgatyocaturmano yājayāva tveti kenetyanenarṣabheṇeti tatheti tasyālabdhasya sa vāgapacakrāma

These two said, 'God-fearing, they say, is Manu: let us two then ascertain!' They then went to him and said: 'Manu! we will sacrifice for thee!' He said: 'Wherewith?' They said: 'With this bull!' He said: 'So be it!' On his (the bull's) being killed the voice went from him.